1. Field of the Disclosure
The present disclosure generally relates to a design of an integrated circuit, and more particularly to an active transformer power amplifier structure.
2. Description of the Related Art
As communication technologies such as mobile phones, the internet, and digital televisions become more popular, there is an increased need for a high quality and low cost power amplifier. However, problems with the current complementary metal-oxide-semiconductor (“CMOS”) process may include low breakdown voltages and high substrate loss of silicon. Therefore, an approach to power synthetic through a transformer is proposed in order to reduce the area of transistors as well as increase the output power. However, a conventional transformer structure requires a large secondary winding when integrating multiple transistors or doing high ratio impedance transforms, which will cause the Q factor value to decrease. This problem becomes more severe when integrating additional transistors.
One way to address this issue is by implementing a discrete-type active transformer structure, which has the advantages of excellent characters and good impedance matching. However, it still encounters consuming large layout area problem when using a large number of transistors. In addition, the lack of design flexibility of the discrete-type active transformer structure makes it difficult to implement in the system in on-chip applications.